iStock/Thinkstock(WASHINGTON)-- Three U.S. military service members were killed and two others were wounded Wednesday in an ambush in Niger, according to a U.S. official. The American troops were on a regular joint patrol with Nigerien troops in a border area known for radical terror activity.

A group of about 10 to 12 American service members were accompanying Nigerian soldiers on a regular patrol late Wednesday afternoon when they came under attack according to the U.S. official.

Three American service members were killed in the ambush and two others were wounded, said the official. The wounded Americans were taken to Niamey, Niger's capital, for medical treatment.

The ambush took place about 200 kilometers (125 miles) north of Niamey, close to the border with Mali in an area where Al Qaeda in the Maghreb and other ISIS affiliated groups have been active. The official said it is unknown who attacked the joint U.S.-Nigerien patrol.

President Trump was briefed on the attack by John Kelly, the White House Chief of Staff, according to White House Press Secretary Sarah Sanders

U.S. Africa Command acknowledged that U.S. forces had come under attack on Wednesday, but did not confirm any U.S. casualties.

"We can confirm reports that a joint U.S. and Nigerien patrol came under hostile fire in southwest Niger," said Lt. Commander Anthony Falvo, a spokesman for U.S. Africa Command. "We are working to confirm details on the incident and will have more information as soon as we can confirm facts on the ground."

There are about 400 U.S. military personnel in Niger most of whom work at two drone bases, in Niamey and Agardez in northern Niger, providing reconnaissance information to the Nigerien military to counter violent extremist groups.

The U.S. personnel who came under attack were part of the effort to help the Nigerien military improve their counter-terrorism capabilities.